PMC

Mutations in human CYP7B1 gene. Exons are indicated by shaded boxes drawn to scale. Introns are indicated by dashed lines and are not drawn to scale. Transcript coding regions are shaded blue; 5′- and 3′-untranslated regions are white. Mutations in subjects with liver failure are shown above the gene; those found in spastic paraplegia type 5 are shown below the gene.

CYP7B1 and reactions catalyzed. A, schematic of the 506-amino acid enzyme showing regions encoded by the six exons of the gene and the positions marked by arrows at which five introns interrupt individual codons. The heme cofactor is covalently bound to Cys⁴⁴⁹. B, 7α-hydroxylation of substrates (1, pregnenolone; 2, dehydroepiandrosterone; 3, 25-hydroxycholesterol; 4, 27-hydroxycholesterol) and 6α-hydroxylation of 5α-androstane-3β,17β-diol. POR, cytochrome P450 oxidoreductase.